[PD] smallest possible value of a delay-time

Miller Puckette mpuckett at man104-1.ucsd.edu
Fri May 14 17:45:49 CEST 2004

Fascinating question... You can get very small delays from allpass
filters, but they're frequency-dependent (i.e., the group phase delay
depends on frequency.)  There are probably other interpolation schemes that
could get fractional delays (fit a polynomial through the points you have,
1 to the right and n-1 to the left, for instance) but they won't have
a flat frequency response.  So one could probably devise trade-offs that
sounded OK, at least at low frequencies.

If the aim is to make a recirculating delay network with very low delay, the 
best way is probably to resample to a much higher sample rate, do the job, and
then resample back down.


On Fri, May 14, 2004 at 11:28:16AM -0400, Larry Troxler wrote:
> On Fri, 14 May 2004, Frank Barknecht wrote:
> > Thinking of tapes as simple sample recorder/players or even as some
> > kind of adc/dac combination, they must follow the same rules as other
> > samle players, that is: the max frequency they can record or play is
> > Nyquist frequency, that is half sample rate. The shortest possible
> > delay time then in theory is 1/nyquist[Hz] seconds.
> >
> Is it? Using a fractional interpolating all pass filter, you can't
> acheive delays less than one sample? Or does the allpass filter let you
> get fractional delays, but still the minimum delay is one sample?
> Larry Troxler
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